Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque

h, w = map(int, input().split())
Map = [['#'] * (w+2)]
Map += [['#'] + list(input()) + ['#'] for _ in range(h)]
Map += [['#'] * (w+2)]

cnt = 0

for i in range(h+2):
    for j in range(w+2):
        if Map[i][j] == '.':
            cnt += 1
            
stack = deque([(1,1)])
Map[1][1] = 1
moved = [[0,1], [0,-1], [1,0], [-1,0]]

while stack:
    x, y = stack.popleft()
    for s, t in moved:
        if Map[x+s][y+t] == '.':
            stack.append((x+s, y+t))
            Map[x+s][y+t] = Map[x][y] + 1

goal = Map[-2][-2]
if goal == '.':
    print(-1)
else:
    print(cnt - goal)